(1) Field of the Technology
The present technology relates to a toner cartridge for use in an image forming apparatus such as a laser beam printer, multifunctional machine or the like and an image forming apparatus using this cartridge, in particular relating to a toner cartridge for storing toner such as a replaceable toner hopper, toner bottle, etc., as well as relating to an image forming apparatus using the cartridge.
(2) Description of the Prior Art
Conventionally, image forming apparatuses using static electrophotography usually include the steps of charging, exposure, development, transfer, separation, cleaning, charge erasing, fixing and the like.
In an image forming apparatus thus configured, the process for image forming is achieved as follows. That is, the surface of a photoreceptor that is rotationally driven is uniformly electrified by a charging device (charging step). Then, the photoreceptor surface thus electrified is illuminated with a laser beam from an exposure device to form an electrostatic latent image (exposure step). Subsequently, the electrostatic latent image on the photoreceptor is developed by a developing device to form a toner image on the photoreceptor surface (developing step). The toner image on the photoreceptor is transferred to a transfer medium by a transfer device (transfer step), then the toner image is heated by a fixing device and fixed to the transfer medium (fixing step). On the other hand, the residual toner remaining on the photoreceptor drum surface after the transfer step is removed by a cleaning device and collected into a predetermined collecting portion (cleaning step). The photoreceptor surface after cleaning is cleared of residual charge by a charge erasing device to prepare for a next image forming operation (charge erasing step).
As the developer for developing the electrostatic latent image on the photoreceptor, a mono-component developer consisting of a toner only or a dual-component developer consisting of a toner and a carrier is usually used.
Since a mono-component developer does not include any carrier, there is no need to have an agitating mechanism for mixing toner and carrier uniformly. Hence the developing device has the advantage of a simple structure. However, there is a drawback that the amount of static charge on the toner is unlikely to be stable.
On the other hand, since a dual-component developer needs to have an agitating mechanism for mixing the toner and carrier uniformly, there is a drawback that the developing device is complex. However, since the developer presents stable toner charging performance and suitability to high-speed machines, it is often used for high-speed image forming apparatuses and color image forming apparatuses.
Recently, in order to meet the demands of the users for energy saving and high-quality image printing, micro toners having a low softening temperature and a volume mean diameter as low as 5 to 9 μm have become used.
Though the toner of this kind is designed to be able to be fixed at low temperatures and is effective in enhancing resolution and reducing granulation to achieve improved image quality, the toner is low in fluidity so that there occurs the problem that it is difficult to control the amount of toner supplied from the toner cartridge to the developing device.
Particularly, there are some configurations in which external additives are added in order to improve the fluidity of the toner. In such a case, however, when a sponge-formed supply roller is used as the toner discharging member for the toner cartridge, the external additives become embedded into the toner particles due to friction between the toner and the sponge-formed supply roller, causing the problem that the fluidity becomes extremely lowered.
As the prior technology to deal with this problem, there has been a disclosed conventional configuration in which a screw-formed agitating and conveying member is used to perform toner supply (see patent document 1: Japanese Patent Application Laid-open 2001-83802). As another disclosure, there has been a configuration in which a screw-formed toner discharging member is used instead of a spongy-formed supply roller so as to reduce friction between the toner and the supplying member during toner supply (see patent document; Japanese Patent Application Laid-open 2008-216360).
However, when the toner that is low in fluidity after having been left for long time under a high temperature environment is conveyed and agitating by rotating a screw-formed toner discharging member as described in patent document 1, the toner is compressed without being discharged from the toner discharge port, causing the problem that the toner discharging member becomes stuck (or referred to as ‘locked’ hereinbelow).